This section is intended to provide a background or context to the invention disclosed below. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived, implemented or described. Therefore, unless otherwise explicitly indicated herein, what is described in this section is not prior art to the description in this application and is not admitted to be prior art by inclusion in this section. Abbreviations that may be found in the specification and/or the drawing figures are defined at the end of the specification but prior to the claims.
Some example embodiments herein relate to a problem of exchanging signal samples among nodes in a wireless network with a non-ideal backhaul network. This exchange of information is essential to enable cooperative uplink reception. This can happen in various deployment scenarios, such as in macro networks with an X2 interface used for inter-BS interconnect, a cluster of small cells in dense environment, or heterogeneous deployment with a distributed backhaul network.
The backhaul network is required to exchange signal samples from a “helper” cell to a “recipient” cell for cooperative uplink reception. That is, one user equipment's transmission is received by both the helper cell and the recipient cell. The recipient cell will perform analysis on information received by itself and by the helper cell. The exchange of information between helper and recipient cells is either by circuit-switched or packet-switched backhaul networks, depending on architecture and deployment. Generally, the backhaul network is considered without any delay in information exchange, but this is not true in a real scenario. If the delay is small, less than one ms, the information can be utilized by the recipient cell to decode user data. If the delay is larger, e.g., five or 10 ms, this becomes a bottleneck, as the scheduler in the recipient cell needs to wait to decode user data. In LTE, there is a fixed time on the delay for transmitting an ACK/NACK to the user, which may be violated if the information from the helper cell arrives with a larger delay.
Standard UE behavior is that if the UE receives an ACK, the UE does not retransmit a packet to abase station. However, if later the UE receives an UL grant for the same packet (e.g., as indicated by the same NDI bit), the UE will retransmit the packet. The primary purpose (one might assume) of specifying this behavior is to account for the case where the base station sent an ACK, but the UE interpreted the ACK as a NACK (and therefore sent no retransmission).